Power supply systems are pervasive in many electronic applications from computers to automobiles. Generally, voltages within a power supply system are generated by performing a DC-DC, DC-AC, and/or AC-DC conversion by operating a switch loaded with an inductor or transformer. One class of such systems includes switched mode power supplies (SMPS). An SMPS is usually more efficient than other types of power conversion systems because power conversion is performed by controlled charging and discharging of the inductor or transformer and reduces energy lost due to power dissipation across resistive voltage drops.
An SMPS usually includes at least one switch and an inductor or transformer. Some specific topologies include buck converters, boost converters, and flyback converters, among others. A control circuit is commonly used to open and close the switch to charge and discharge the inductor. In some applications, the current supplied to the load and/or the voltage supplied to the load is controlled via a feedback loop.
In some power supply applications, a switched mode power supply may be operated in two modes of operation: pulse frequency modulation (PFM) and pulse width modulation (PWM). During PFM, the frequency of control signals applied to the switch(es) may be modified according to some control logic and a feedback signal. During PWM, the pulse width of control signals applied to the switch(es) may be modified according to the control logic and feedback signal.